From d0ccea04045e9b154970a92f8eafa0c76cb0f2e2 Mon Sep 17 00:00:00 2001
From: Simon Frei <freisim93@gmail.com>
Date: Tue, 3 Nov 2020 19:09:32 +0100
Subject: [PATCH] lib/config: Sanity checks on MaxConcurrentWrites (ref #7064)
 (#7069)

---
 lib/config/config_test.go         |  1 +
 lib/config/folderconfiguration.go | 12 +++++++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/lib/config/config_test.go b/lib/config/config_test.go
index 0008d5c83..3d73912e4 100644
--- a/lib/config/config_test.go
+++ b/lib/config/config_test.go
@@ -129,6 +129,7 @@ func TestDeviceConfig(t *testing.T) {
 				WeakHashThresholdPct: 25,
 				MarkerName:           DefaultMarkerName,
 				JunctionsAsDirs:      true,
+				MaxConcurrentWrites:  maxConcurrentWritesDefault,
 			},
 		}
 
diff --git a/lib/config/folderconfiguration.go b/lib/config/folderconfiguration.go
index 4c08b9d12..d92dd67f8 100644
--- a/lib/config/folderconfiguration.go
+++ b/lib/config/folderconfiguration.go
@@ -26,7 +26,11 @@ var (
 	ErrMarkerMissing    = errors.New("folder marker missing (this indicates potential data loss, search docs/forum to get information about how to proceed)")
 )
 
-const DefaultMarkerName = ".stfolder"
+const (
+	DefaultMarkerName          = ".stfolder"
+	maxConcurrentWritesDefault = 2
+	maxConcurrentWritesLimit   = 64
+)
 
 func NewFolderConfiguration(myID protocol.DeviceID, id, label string, fsType fs.FilesystemType, path string) FolderConfiguration {
 	f := FolderConfiguration{
@@ -206,6 +210,12 @@ func (f *FolderConfiguration) prepare() {
 	if f.MarkerName == "" {
 		f.MarkerName = DefaultMarkerName
 	}
+
+	if f.MaxConcurrentWrites <= 0 {
+		f.MaxConcurrentWrites = maxConcurrentWritesDefault
+	} else if f.MaxConcurrentWrites > maxConcurrentWritesLimit {
+		f.MaxConcurrentWrites = maxConcurrentWritesLimit
+	}
 }
 
 // RequiresRestartOnly returns a copy with only the attributes that require